This weekend, Kurt Anderson's Studio 360 did a few stories on the film's anniversary. They even did an interview with the former Playboy bunny who claims she was the one who got knifed in the shower. Marli Renfro has for years said that she was Janet Leigh's body double for the majority of this iconic scene. However, Leigh has stuck to her story that she was there for all 77 camera setups, shot over the course of 6 days in December 1959. But Marli makes a good case in her interview. Also, given Hollywood's long standing use of body doubles and any actors natural inclination to complain about standing naked in a shower for a week, I'm inclined to believe Marli's story.
If you'd like to read more about the making of this extraordinary film, the Wikipedia entry is very comprehensive. And there are a number of books on the subject, notably Donald Spotos' "The Dark Side of Genius
", "Alfred Hitchock and the Making of Psycho
" and the The Truffaut Interviews 
which are probably the best in that you get to hear everything direct from the director himself.
